Details for "Water Equivalency Test Method?"

I am performing a design on an existing system that was 3% AFFF and we are converting it to 3x3 NFF. Bladders, proportioners, concentrate lines are being replaced and all sprinklers being replaced to meet the specification for the new concentrate.

In the spec it has been requested to utilize the "water equivalency test method," which is outlined in NFPA 11.

I've performed installs, inspections of foam systems for 10+ years, I've never seen this method installed and not very versed in how it really works, only from what I've read. There's not much information out there.

Have you used this method?

What have the requirements been for testing this method?

Were you given outside specifications? Does any additional information exist for detail?

I'm wanting to be sure we're compliant from a design and install perspective.

I'm following the diagram supplied in NFPA 11-2016.

"D.5.2.3 Water Equivalency Method. In this approach, water issued as a surrogate liquid in place of foam concentrate. The initial acceptance test(s) are conducted with the actual foam concentrate using equipment similar to that shown in Figures Figure D.5.2.2(b) and Figure D.5.2.2(c): real-time pressure, flow, and conductivity measurements are recorded with the actual foam concentrate to determine that the system is pro-portioning accurately. Immediately following this test, a water equivalency test at the exact same pressure and flows as in the initial foam discharge test is performed after isolating the foam concentrate tank. Example test setups are shown in Figures Figure D.5.2.3(a) and Figure D.5.2.3(b). This provides a baseline for comparison using water only for follow-on routine inspections and tests."

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